# What does my A1C mean?

Converts an A1C result to estimated average glucose (ADAG equation, mg/dL and mmol/L) and to IFCC mmol/mol, or back, and shows the CDC range: normal, prediabetes, or diabetes.

- Page: https://www.acalculator.org/health/a1c-calculator
- JSON spec: https://www.acalculator.org/health/a1c-calculator.json
- Version: 64ef9ef548a2

## Default answer

Example with the default inputs (A1C 7%): An A1C of 7% means an estimated average glucose of 154 mg/dL (8.6 mmol/L).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| a1c | A1C | Hemoglobin A1C in percent (NGSP units), as a US lab reports it. |
| eag | Average glucose (mg/dL) | Estimated average blood glucose over about 3 months, in milligrams per decilitre. |
| mmol | Average glucose (mmol/L) | Estimated average blood glucose over about 3 months, in millimoles per litre. |
| ifcc | A1C (mmol/mol) | Hemoglobin A1C in IFCC units, millimoles per mole, as labs outside the US report it. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| a1c | A1C | Hemoglobin A1C in percent (NGSP units), with its CDC range. |
| eag | Average glucose (mg/dL) | Estimated average glucose in mg/dL: 28.7 × A1C − 46.7 (ADAG study). |
| eagMmol | Average glucose (mmol/L) | Estimated average glucose in mmol/L: the mg/dL value ÷ 18.0156. |
| ifcc | A1C (mmol/mol) | A1C in IFCC units: (A1C − 2.15) ÷ 0.0915. |
| range | Range | The CDC A1C range: normal below 5.7%, prediabetes 5.7% to 6.4%, diabetes 6.5% or above. |

## Method

eAG (mg/dL) = 28.7 × A1C − 46.7 (ADAG); eAG (mmol/L) = eAG (mg/dL) ÷ 18.0156; A1C (IFCC, mmol/mol) = (A1C − 2.15) ÷ 0.0915.

## Assumptions

- A1C is in NGSP percent units, the unit US labs report.
- The eAG equation is the average relationship found in the ADAG study; one person’s average glucose can differ from it.
- Blood loss, transfusion, iron-deficiency anemia, kidney failure, liver disease, and some hemoglobin variants can make an A1C result wrong (NIDDK).
- The ranges are the CDC’s diagnostic ranges for adults. They are not treatment targets, and this is not medical advice.

## Worked examples

1. a1c = 6% gives eag = 125.5, mmol = 6.966185, ifcc = 42.076503, range = Prediabetes. Source: Nathan and others (2008), ADAG study: eAG = 28.7 × A1C − 46.7, so 6% is 125.5 mg/dL; mmol/L and IFCC by hand in content.mdx; CDC: 5.7% to 6.4% is prediabetes.
2. a1c = 7% gives eag = 154.2, mmol = 8.559249, range = Diabetes. Source: Nathan and others (2008): 28.7 × 7 − 46.7 = 154.2 mg/dL; CDC: 6.5% or above is the diabetes range.
3. eag = 154 gives a1c = 6.993031%. Source: hand calculation in content.mdx: A1C = (154 + 46.7) ÷ 28.7 = 6.99%, the ADAG equation solved for A1C.
4. a1c = 5.7% gives ifcc = 38.797814, eag = 116.89, range = Prediabetes. Source: Hoelzel and others (2004): NGSP = 0.0915 × IFCC + 2.15, so 5.7% is (5.7 − 2.15) ÷ 0.0915 = 38.8 mmol/mol; CDC: 5.7% starts the prediabetes range.
5. ifcc = 48 gives a1c = 6.542%, range = Diabetes. Source: Hoelzel and others (2004): 0.0915 × 48 + 2.15 = 6.542%; CDC: 6.5% or above is the diabetes range.

## FAQ

### How do I convert A1C to average blood sugar?

Use the ADAG study equation: estimated average glucose (mg/dL) = 28.7 × A1C − 46.7. An A1C of 7% gives 28.7 × 7 − 46.7 = 154.2 mg/dL. To get mmol/L, divide the mg/dL value by 18.0156: 154.2 ÷ 18.0156 = 8.6 mmol/L.

### What A1C level is normal?

The CDC lists an A1C below 5.7% as normal, 5.7% to 6.4% as prediabetes, and 6.5% or above as diabetes. A diagnosis needs a health care provider, usually with a repeat test.

### What is A1C in mmol/mol?

Labs outside the US often report A1C in IFCC units, millimoles per mole. The two scales are linked by NGSP % = 0.0915 × IFCC + 2.15 (Hoelzel and others, 2004). So 6.5% is (6.5 − 2.15) ÷ 0.0915 = 47.5, which labs round to 48 mmol/mol.

### Why does my meter average not match my A1C?

A1C reflects glucose over about 3 months, while a meter average depends on when you test. People also differ: the ADAG equation is an average, and one person's glucose can sit above or below it. NIDDK notes that recent blood loss, transfusion, iron-deficiency anemia, kidney failure, liver disease, and some hemoglobin variants can make an A1C result wrong.

### What is the difference between eAG and GMI?

eAG turns a lab A1C into an average glucose. The glucose management indicator (GMI, Bergenstal and others, 2018) goes the other way: it turns the average glucose from a continuous glucose monitor into an estimated A1C, with its own equation. GMI and a lab A1C often do not agree exactly.

### How often should A1C be checked?

That depends on your situation, so ask your health care provider. A1C changes slowly, because it reflects about 3 months of glucose, so a new result usually needs a few months to show a change.

## Sources

- Nathan DM, Kuenen J, Borg R, et al. (A1c-Derived Average Glucose Study Group). Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31:1473–1478. doi:10.2337/dc08-0545
- Hoelzel W, Weykamp C, Jeppsson JO, et al. IFCC reference system for measurement of hemoglobin A1c in human blood and the national standardization schemes in the United States, Japan, and Sweden: a method-comparison study. Clinical Chemistry 2004;50:166–174. doi:10.1373/clinchem.2003.024802
- Centers for Disease Control and Prevention, Diabetes Testing (last reviewed May 15, 2024). https://www.cdc.gov/diabetes/diabetes-testing/index.html
- National Institute of Diabetes and Digestive and Kidney Diseases, The A1C Test & Diabetes (last reviewed April 2018). https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test
- Bergenstal RM, Beck RW, Close KL, et al. Glucose Management Indicator (GMI): a new term for estimating A1C from continuous glucose monitoring. Diabetes Care 2018;41:2275–2280. doi:10.2337/dc18-1581
- IUPAC Commission on Isotopic Abundances and Atomic Weights, Abridged standard atomic weights (2021): C 12.011, H 1.008, O 15.999. https://ciaaw.org/abridged-atomic-weights.htm